When buying in bulk, there’s an implied promise that you’ll pay less per unit than if you bought a smaller amount. That’s one of Costco’s strategies to generate profits—offering deals to its members.

However, sometimes that promise is broken. It must have happened to you at least once: you look at a “family size” box of cookies or cereal at the grocery store only to discover it actually costs more per ounce than purchasing a smaller container. So it’s a bit deceiving to know that buying in bulk doesn’t always save you money.

At Costco, the chain that holds the monopoly on bulk purchase deals, some products are more costly per unit than regular-sized products. Others are comparably priced or cheaper but will likely expire before you can eat or finish them. Still, others are sold at a low price but fall short regarding quality.

So, we’ve done a bit of research and found out which products are actually more expensive at Costco. Much to our surprise, we realized that buying Kirkland products in bulk from Costco doesn’t save you any money! In fact, you end up paying more than if you were to buy those items directly from Kirkland.

To help you make the best decision, here are 7 products you may want to skip while bulk buying at Costco.

1. Laundry Detergent

Prices per ounce for huge tubs of dish soap, laundry detergent, and other cleaning products are usually lower at Costco than at Walmart, Target, or Amazon. However, the stuff in those giant Costco containers has an expiration date.

Unopened cleaning supplies (such as detergents) have a shelf life of between nine and 12 months. Once you open them, they are good for only about six months. Moreover, if you use laundry powder in an environment with high levels of humidity, the number is even lower.

Buying laundry detergent from Costco is a great idea for large families that wash many clothes. Also, if you only live with your spouse but both of you workout a lot, going for the Costco option may be ideal. But if you use detergent more slowly, you will either waste money or have dirtier clothes.

2. Parts

You won’t find appliance components or automotive parts at Costco, but you can often purchase water filters for your fridge, ink for your printer, air filters for your furnace, and similar things you need to replace routinely.

If you’ve been buying these types of things from Costco, we’re here to give you a second option—a more affordable one. Try looking for them at Kirkland, where you’re more likely to find lower prices.

Or even better, to make sure you get these at their best price, buy them directly from the parts clearinghouses, manufacturers, or a local business that overhauls your appliances.

Another option would be to check the Amazon website, especially if you have a Prime membership.

3. Organic Milk

If you don’t eat meat and dairy or you simply like the plant-based alternatives to milk, you’re probably buying organic milk weekly when you do grocery shopping.

A three-pack of cow milk is usually an excellent deal at Costco, but plant-based milk is less reliably affordable. We did some research and discovered that a three-pack of Kirkland Signature 1% organic milk at Costco costs several bucks more than three single-gallon milk containers at Target.

This often applies to soy milk, almond milk, and similar options beyond 1%, 2%, and whole milk. When you think about how quickly milk goes bad (whether it’s regular or organic), you realize you’re usually better off not buying this product in bulk.

4. Cooked and Take-and-Bake Meats

Grocery stores across the world have a smart strategy that helps them make a lot of profit: impulsive buying. There was even a study conducted in 2018 that showed how much we spend monthly on impulse purchases. Are you ready to be shocked?

The answer is $400! That’s a lot!

Those sauced-up spare ribs, pop-in-the-oven pizzas, and rotisserie chickens are among the products that tempt us, the customers, the most. They look like a tasty meal and feel like a good deal. However, you may want to skip them when you do grocery shopping at Costco, as they are more expensive than the same option at Kirkland or other grocery stores.

Costco executives are very aware that a trip to their gigantic store can be exhausting, so they rely on the impulse purchases that exhaustion fosters.

5. Produce

Frozen meats, canned soup, dried goods, and snacks are great deals at Costco. However, pay attention when evaluating those giant boxes and bags of produce. They are rather suitable for the restaurant industry and significant catering events, which cook much more food than you do at home. So ask yourself if your family will eat three heads of broccoli before the flower buds begin to wilt.

As with the laundry detergent we mentioned on No. 1, the price per unit is only a great deal if you use what you purchased before it expires. Unless you’re going to cook the produce promptly, only your compost pile will benefit.

But that’s not all; many produce items you find at Costco cost more per unit than the alternatives at Kirkland or other local grocery stores. However, this changes season by season and case by case, so make sure you do your research before buying.

6. Single-Item Offerings

Costco makes lots of money and gets savings on bulk purchases. The warehouse club buys large packages and cuts customers in on the savings. In other words, you should be skeptical of anything the store tries to sell you in single-item form.

This doesn’t apply to every product, however. Costco vacation packages and car deals are reliably less expensive than you would spend on the exact same item at a regular store.

That’s why the best thing you can do when seeing a single item offered at Costco is to use your mobile phone to compare prices elsewhere. It’s a great strategy to ensure it’s a really good deal.

7. Diapers

Parents who need diapers tend to fall short on energy and time, so it’s tempting to purchase them and other similar baby supplies during your Costco trip when you do grocery shopping. However, most retailers have comparable or better prices on diapers.

At Costco, the price for a package of 192 Kirkland Brand Diapers (size 1-2) is $35.99, which means you pay 18 cents per unit. On the other hand, a package of 37 Up&Up Brand Diapers (size 1 or 2) at Target is $3.79 (13 cents per unit). Also, a package of Parent’s Choice Diapers (size 1) at Walmart costs $16.47 for 168, which would be just 9.8 cents per unit.

Moreover, Amazon Family, a branch of Amazon Prime, gives you the chance to purchase the supplies you need for your baby in bulk, offering you a 20% discount on products comparable to Costco’s prices. These come with the extra benefit of getting them regularly without leaving the house.

But what are the items you should always buy from Costco? Keep reading to find out!

Reliable Costco Savings

We’d be remiss if we only focused on what not to buy at Costco. Although your grocery shopping experience will vary, as will prices throughout different seasons, some products are reliably less expensive when you purchase them here.

Take breakfast cereals, for example. Though you’ll need a large family to finish the package before it goes stale, you will pay around 75% of the price at Target for the equivalent purchase. Spices are also cheaper at Costco; McCormick-brand spices come in at about two-thirds of what you’d pay at Walmart.

If you love coffee, you’ll also want to buy the Kirkland brand pods at Costco; they are high-quality and come for just over half what you would pay at Walmart for a comparable brand. Gas is also a few cents cheaper at Costco compared to elsewhere. Moreover, the store’s cash-back program adds up to 6% in combined savings between rebates and reduced prices.

This being said, make sure you do a bit of research before bulk buying at Costco, but keep in mind that some items are cheaper here than elsewhere.

You may also want to read Sam’s Club Products: 6 You Should Avoid Buying There.